1. Field of the Invention
The present invention relates to a method for manufacturing a thermal head or an ink jet recording head. More particularly, the invention relates to a method for manufacturing a lengthy recording head with integrally housed semiconductor functional elements comprising diodes, transistors, or the like.
2. Related Background Art
There is known an ink jet recording head provided with a transistor integrally housed therein as disclosed in U.S. Pat. No. 4,429,321.
This ink jet recording head is of the constitution shown in FIG. 16. FIG. 16 is a schematic cross section view illustrating the constitution of the ink jet recording head.
In FIG. 16, numeral reference 801 stands for the entire element bearing member provided with transistors 810. On the element bearing member 801, there is disposed a top plate member 829 capable of serving to form an ink discharging outlet 823, a liquid pathway 822 and a common liquid chamber 824. Numeral reference 808 stands for an ink feed pipe connected to the common liquid chamber 824.
The element bearing member 801 comprises a p-type semiconductor region 815 and an n.sup.- -type semiconductor region 819 disposed on the p-type semiconductor region 815. Numeral reference 830 stands for an isolation region which serves to isolate the n.sup.- -type semiconductor region 819 from the constituent n.sup.- -type semiconductor region 825 as a highly resistive layer of the transistor 810. The isolation region 830 is comprised of a potion extending from the p-type semiconductor region 815.
The transistor 810 comprises a collector region comprising said highly resistive layer 825, an n.sup.+ -type semiconductor layer region 828-2, an embedded layer region 828-1, a p-type base region 826, and an n.sup.+ -type emitter region 827.
On the surface side of the element bearing member 801, there are provided a heat accumulating layer 818, a heat generating resistive layer 820, a common electrode 809, an individual electrode 811, a base electrode 813, an emitter electrode 814, an insulating layer 817, and a protective layer 821. Numeral reference 805 stands for an electrothermal transducer provided with a heat generating portion 812.
In the recording head shown in FIG. 16, when a signal is inputted into the base electrode 813 of the transistor 810, the transistor is turned on to allow an electric current to flow in the heat generating resistive layer 820. Thus, heat is transferred to ink in the liquid pathway 822 through the heat generating portion 812 to create at least a bubble due to evaporation of the ink, wherein ink is discharged through the ink discharging outlet 823 by the pressure of the bubble created.
The recording head shown in FIG. 16 is fabricated in the following manner. That is, the embedded layer region 828-1 is firstly formed on a p-type single-crystal member capable of serving as the p-type semiconductor region 815 by means of a conventional ion implantation technique, followed by forming an n.sup.- -type epitaxial layer by way of epitaxial growth. The isolation region 830 is then formed by incorporating a p-type impurity into the corresponding portion of the n.sup.- -type epitaxial layer by means of vapor-phase diffusion technique, whereby (a) an n.sup.- -type epitaxial layer region to be the n.sup.- -type semiconductor region 819 and (b) another n.sup.- -type epitaxial layer region to be the highly resistive layer 825, which are isolated by the isolation region 830 one from another, are established. The base region 826 is formed by implanting boron ions into the corresponding portion of the n.sup.- -type epitaxial layer region (b) by means of ion implantation technique. The emitter region 827 is formed by implanting phosphorous ions into the corresponding portion of the base region 826 formed in the above by means of ion implantation technique. The n.sup.+ -type semiconductor layer region 828-2 which serves as the collector is formed by implanting phosphorous ions into the corresponding portion of the n.sup.- -type epxitaxial layer region (b) by ion implantation technique.
Subsequently, a silicon oxide layer as the heat accumulating layer 818 is formed by means of thermal oxidation technique. A hafnium boride layer as the heat generating resistance layer 820 is then formed by means of a sputtering technique. Thereafter, electrodes 809, 811, 813 and 814 respectively comprised of aluminum are formed respectively by means of a sputtering technique.
The recording head shown in FIG. 16 is fabricated by fixing the top plate member 829 to the element bearing member 801 obtained in the above as illustrated in FIG. 16.
Now, there is an increased demand for reduction in the production cost as for a recording head of this kind. Particularly, as for the active element used in the circuit which drives the electrothermal transducer serving as the heater for discharging ink, the production cost becomes unavoidably high in the case where an integrated circuit (IC) is externally disposed. In order to attain the reduction in the production cost, it is desirable to integrate such element with the element bearing member in which the electrothermal transducer is to be formed as in the case of the recording head shown in FIG. 16.
However, in order to accomplish such integration as desired without reduction in the characteristics required, it is necessary to use a high quality semiconductor.
As long as a small-sized recording head which can be fabricated using a single-crystal silicon wafer is concerned, it is possible to provide at a relatively low production cost such small-sized recording head capable of displaying a sufficient performance even if it is of the constitution shown in FIG. 16.
The constitution shown in FIG. 16 is, however, almost impossible to be applied in the fabrication of a lengthy recording head having a wide ink discharging outlet surface equivalent to the width of a large-sized recording medium, for example, of A-4 size. This is due to the fact that a commercially available single-crystal silicon wafer is a disc of 6 to 8 inches in diameter and because of this, it is impossible to attain the fabrication of such lengthy recording head as above mentioned using such small-sized single-crystal silicon wafer.
In view of the above situation, the conventional lengthy recording head is structured as shown in FIG. 17. The recording head shown in FIG. 17 comprises a head 852 comprising a thin film resistor formed on a glass substrate which serves as the heat generating portion and a plurality of external functional elements (switching transistors in other words) 850 respectively comprising an IC, wherein the head 852 and the plurality of functional elements 850 are disposed on a common supporting member 854 made of Al for example, and each of the plurality of functional elements 850 is electrically connected to the head 852 by means of a wire 853 for example.
There is also a problem as for the lengthy recording head of the constitution shown in FIG. 17 that the production cost becomes unavoidably high since numerous expensive ICs are used.
In addition, as the thin film semiconductor element in the prior art, there is no choice but to use a limited base member such as a member comprising a so-called SOS (silicon-on-sapphire) or a member comprising a so-called SIMOX which has an insulating region comprising silicon oxide in a semiconductor wafer, and because of this, it is almost impossible to provide a recording head at a reduced production cost.
Thus, there is an increased demand for provision of an appropriate method which makes it possible to efficiently fabricate not only a desirable lengthy recording head but also an improved recording head having highly functional semiconductor elements integrally housed therein at a reduced production cost.